Reforming with a coprecipitated platinum-lead catalyst

ABSTRACT

METHOD OF PRODUCING AROMATIC HYDROCARBONS WHICH COMPRISES HYDROFORMING A HYDROCARBON AT A TEMPERATURE FROM 300*C. TO 650*C. OVER A CATALYST COMPRISING PLATINUM AND LEAD AND PREPARED BY A COPRECIPITATION PROCEDURE.

g- 5, 1974 NAOYA KOMINAMI ETAL- ,8 7,973

REFORHING WITH A COPREQIPITATED PLATINUM-LEAD CATALYST Filed. Nov. 18, 1971 AROIVIATICS YIELD 2 3 4 5 6 Q Fft Un t "sees P fi ABSTRACT OF THE DISCLOSURE Method of producing aromatic hydrocarbons which comprises hydroforming a hydrocarbon at a temperature from 300"- C. to 650 C; over a catalyst comprising platinum and leadand prepared by a coprecipitation produ .1. .i.

I -RELATED APPL'ICATIONS ..This application is a continuation-in-part of our application Ser. No. 6,948, filed Jan. 29, 1970. It is related to applications; Ser. No. 200,064 which describes hydroforming of a hydrocarbon charge with a Pt-Pb catalyst prepared by impregnation procedures; Ser. No. 200,065 which is directed-to the catalysts of Ser. No. 200,- 064; and Ser. No. 200,023 which. describes hydroforming eta-hydrocarbon charge with a Pt-Pb catalyst prepared by auotherimpregnation procedure; all filed concurrently..herewith.

I BACKGROUND OF THE 'INVENTION I Field of the Invention eThis invention relates to'a method-of producing aromatic-hydrocarbons from pertoleum sources at high yields. More =iparticularly, it is concerned with a method of producinga-distillate: of high aromatic concentration in' 'high' yield by highly-selectively subjecting naphthenic hydrocarbons to dehydrogenation "and'paraffinic hydrocarbons to dehydrocyclization.

1 '5 "DESCRIPTION OF THE PRIOR ART I'Alnumbefiof investigations-have been made heretofore on methods for producing aromatic hydrocarbons from petroleum sources :.to establish several industrial processes employing catalysts comprising platinum, chromina', molybdena and the like. In these processes, naphtha is i1'sed"as the starting matrial, which is subjected to "catalytic reaction in .i'gas phase at a high ternperamre. The liquid product thus produced contains isomers offparafiinic hydrocarbons at a high concentra' tion and is often ased as gasolinefor motor cars, etc. because'of its higli octane number, However, its content of aromatic hydrocarbons is so low that an additional extraction or dealkylation' step, is'needed in order to ob- 'e,' 'xyle"nes" and the like. Inaddition, c hydrocarbons based on the starting is'so low that the operation of these steps is costly. .On the; other hand,, demand. for aromatic hydrocarbons is being increa'sed'rapidly due to rapid growth of industriesrelated .to aromatics such as plastic and synthetic fiber industries. In this respect, it has become necessary to develop a process for producing aromatics in a higher yield. Moreover, the gasoline industry needs higher and higher octane numbers.

However, the existing processes will be associated with more expensive products if the yield of aromatics or the octane number is improved, and they are hardly feasible from the industrial point of view. Cracked gaso-' line, a by-product in the production of ethylene, which is one of the favorable sources for aromatics, is limited in 'the amount of production because it depends upon the production of ethylene.

SUMMARY OF THE INVENTION As a result of extensive investigations on the process commercially advantageous in consideration of the source and demand of aromatics as well as the process economy as mentioned above, we have discovered a process with many advantages including the improved yield of aromatics. The present invention, derived from the discovery, is concerned with a method of producing aromatic hydrocarbons which comprises treating a hydrocarbon or a hydrocarbon mixture at a temperature from 300 C. to 650 C. over a catalyst comprising platinum and lead or a catalyst comprising platinum, lead and at least a member selected from lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, zinc, cadmium, mercury, germanium, bismuth, chromium, molybdenum, tungsten, uranium, rhenium, ruthenium, rhodium, palladium, osmium and iridium. The catalyst is prepared by a coprecipitation method.

According to this invention, a variety of advantages may be enjoyed as compared with prior methods as set forth below.

First, benzene, toluene, xylenes and polymethylbenzones are produced by quite simple procedures at low cost because of high concentration and yield of aromatics in the reformate produced according to this invention. For example, a distillate of higher boiling point than toluene or xylene in the reaction product contains neither parafiin nor naphthene and then separation can be effected by distillation only, without application of solvent extraction. Such a distinction from the prior processes is ascribed to high activity and selectivity of the catalyst of this invention in terms of aromatic formation, namely dehydrogenation or dehydrocyclization reactions.

In other words, in the conventional reforming processes known heretofore, since hydrocracking, isomerization, dehydrogenation or dehydrocyclization are the main reactions involved, an attempt to obtain a liquid fraction having a high aromatic concentration leads to an increase in hydrocracking with attendant results in low liquid yield and degraded economy. It on the other hand, the liquid yield is made higher, then the parafiin, concentration in the resulting liquid becomes higher. However, when the catalyst of. the present invention is employed, quite unexpectedly, vhydrocracking and isomerization are suppressed remarkably while dehydro generationof naphthene or dehydrocyclization of parafiin occurs preferentially, and, in addition, the catalyst activity is quite high. v

While lead has been shown to be a poison for a platinum catalyst in hydroforming catalysts (US. Pat. No. 3,000,811 of .Murray et al.), it has been found that particular Pt-Pb combinations containing specified Pb contents in specified Pb/Pt ratios are excellent hydroforming catalysts. If the amount of Pb supported on a carrier with Pt is excessive, Pb exhibits a poisoning eifect. Also, if the ratio of Pb to Pt on a carrier exceeds a specified value, then the Pt catalyst is poisoned. Influencing the effectiveness of the catalysts also is the method by which they are prepared. Surprisingly, then, when the amount of Pb is controlled within prescribed limits, the Pb/Pt ratio is also so controlled, and a particular method of preparation is selected, hydroforming catalysts of high activity and high selectivity can be obtained.

Thus, utilization of features of the present invention as descibed above serves to produce aromatics having high carbon numbers from high boiling fractions having high carbon numbers such as, for example, kerosene and gas oil, in high yields. The same thing applies to naphtha and the process of the present invention affords far higher yields in the production of trimethylbenzene, durene and the like than known processes.

Secondly, purity and yield ofhydrogen are so high that hydrogen can be supplied at a low cost.

Thirdly, life of the catalyst of this invention is so long that frequency in regeneration of the catalyst is reduced under normal reaction conditions in industrial operation.

Fourthly, the catalyst of this invention is operative at lower pressures than in the prior processes. As the rate of degradation in activity in the prior catalysts is much more drastic and they become inoperative during long operation, and, therefore, the process on an industrial scale has to be carried out under high pressures. On the contrary, the catalyst of this invention is stable in the course of a long operation to give a high yield of aromatics.

As the platinum component of the catalyst, there may be used, for example, the hydroxide, platinum halides, chloroplatinic acid or hydrate or ammonium salt thereof. Especially preferred are substances containing a halogen.

This is due to the fact that in a compound containing platinum and halogen, the halogen and especially chlorine present in the compound advantageously contribute to the catalytic activity like in other platinum reforming catalysts. The preferable amount of chlorine contained in the catalyst of the present invention is in the range of 0.1- 2.0% by weight and particularly in the range of (LS-4.5% by weight based on the total weight of catalyst components. As the lead component, there may be employed halogenides, inorganic and organic salts, hydroxide, oxide and the like. The element used as the third component may be in the form of its oxide, hydroxide, halide or other inorganic and organic salt or complex. The platinum, lead and the third components may be in the form of a salt containing each of them.

Contents of the platinum, lead and the third components are 0.01% by weight, 0.01-5 by weight and 0-3% by weight, respectively, and preferably 0.1-1% by weight, (Ll-3% by weight and 01% by weight, respectively based on the total weight of catalyst components, with the ratio of lead to platinum ranging from 0.1 to 7 and preferably from 0.3 to 3.0. p

In the present invention, the ooprecipitation method refers to a method wherein a solution of carrier compo nent and catalyst components are mixed and all of the components either form a gel or are precipitated. In a gelati on method, a catalyst is obtained by adding a catalyst active component to an aqueous solution or sol of a carrier component such as, e.g., alumina, silica and silica-alumina, and removing solvent by vaporizing to dryness or spray drying. Alternatively, a pH adjusting agent such as, e.g. aqueous ammonia, may be added to the solution or sol to effect gelation in a short period of time, followed by drying.

In a method according to precipitation, a catalyst active component is dissolved in an aqueous solution of a compound which may be converted into a solid carrier such as, e.g., aluminum chloride, or an aqueous solution of a catalyst active component is-added to an aqueous -solution of the carrier component. Then a neutralizing agent such as, e.g., aqueous ammonia, is added to precipitate both said components followed by drying to obtain a catalyst.

In the coprecipitation method of the present invention, amounts of platinum, lead and a third component contained in the aqueous solution of platinum compound, lead compound and a third component are generally 0.01- 5 wt. percent Pt, 0.01-5 wt. percent Pb..and.0-3 wt. percent third component, preferablyltllel wt. percent Pt,

0.l-3 wt. percent Pb and 0-1 wt.'percent. third compo:

nent. Ratio of Pt to Pb in the solution ranges 0.1 57.0, preferably 0,3-3.0. As with the conventional'catalysts,

the proportion of contents of the-components depends,

for example, upon the type of carrier, surface area,'order of the addition, method of the calcinationand the like. m

In order to increase the activity of the catalyst, the use of a carrier such as silica alumina, alumina, alumina hydrate, silica, zeolite, kaolin, acid clay or bentonite is.

effective and preferable carriers are alumina, silica alumina, zeoliteand the like. p

The hydrocarbons which may be used in the present invention as the starting material-include those mainly comprising parafiins, olefins ,and naphthen e. having .a boiling point within the range of from, 40 to 350 C., which may be used alone or in admixture of two or more kinds. Preferable hydrocarbons are those having from 6 to 12 carbon atoms Most advantageous materialsfromthe industrial standpoint are naphthas having a boiling range of 40 l90 C., kerosene having a boiling range of 160-260 C., andgas oil having a boiling range of 220-350 C. Feeding ratio of hydrogen to hydrocarbon in gas vol ume is from 0.5 to 15 and preferably from 2 to '10. Prior to the reaction, the catalyst may be pretreated with hydrogen at or near the reaction temperature to activate it. Feeding rate of the hydrocarbon in terms of LHSV, which stands for liquid hourly space velocity (the feeding amount of hydrocarbon per unit time, per unit volume of catalyst, in ml.) is from 0.2 to 10 hr.- and preferably from 0.5 to 5 hr."

Temperatures from 300 C. to 650 C., preferably from 430 C. to 580 C., are employed for the reaction. The reaction pressure is dependent upon the desired quality of product and economy and may be optionally chosen within the range of from 1 to 50 kg./cm. and preferably from 5 to 20 kg./cm. In order to improve the space time yield in the commercial production, :the reaction is preferably carried out under an elevated pressure. Y

DESCRIPTION OF PREFERRED EMBODIMENTS hydrogen and n-heptane at a molar ratioof 3:1 at an.

LHSV of 0.5 hr.- under atmospheric pressure, while, maintaining the layer at Ta temperatureof 490,", C. 'I'he.

molar yields of the products were: Benzene 2.4 tol uene 52.3%, xylenes,i.0% .and thetotalarom Example 2 '1 After cc. of the: same catalyst asused in Example 1.

- were reduced with hydrogen at 530 C. forar'i hour, a

gaseous mixture of hydrogen and kerosene having a composition shown below in a feed ratio of 4:1 was continuously passed through the catalyst layer maintained at 510 Cjat an LHSV of 2.0 hr.- under a reaction pressure of 4 kg./cm. (gauge) for 15 hours.

The catalyst was prepared by the following procedure.

The 1000 g. of alumina sol (10 wt. percent assay) were added 100 cc. of a mixed aqueous solution containing chloroplatinic acid in a concentration of 0.0256 mol./ liter and lead nitrate in a concentration of 0.169 moL/liter and heated on an oil bathwith stirring to vaporize-to dryness. The resulting mass on which both of said components were supportedwas'calcined at 550 C. for 5 hours to obtain a catalyst having a composition of 0.5 wt. percent Pt, 3.5 wt. percent Pb and A1 Composition of the starting kerosene (vol percent):

Aromatic hydrocarbons 15.8 Non-aromatic hydrocarbons 84.2 Boiling point: 157-233 C.

As a result, the yields of the reaction products in terms of percent by weight were as follows:

Hydrogen 3.9 C -C hydrocarbon gas 15.6 Parafins and naphthenes C and higher 7 .8 Benzene, toluene and xylenes 6.5 C aromatic hydrocarbon 13.4 Aromatic hydrocarbons C and higher 54.1

The same reaction as described above was repeated using a 'known catalyst comprising 0.5% platinum and 99.5% alumina. The yields of the reaction products in terms of percent by weight were as follows:

C -C hydrocarbon gas 34.5 Paraffins and naphthenes C and higher 26.5 Benzene, toluene and xylenes 19.8 C aromatic hydrocarbon 9.1 Aromatic hydrocarbons C and higher 9.9

Example 3 To 1000 g. of alumina sol (10 wt. percent assay) were added 100 cc. of a mixed aqueous solution containing chloroplatinic acid in a concentration of 0.0256 mol./ liter and lead nitrate in concentrations specified in the following Table. The resulting mixture was heated on a hot bath with stirring to vaporize it to dryness. The resulting mass on which both of said components were supported was calcined at 550 C. for 5 hours.

The resulting catalysts had compositions of: 0.5 wt. percent Pt, 0.152.5 wt. percent'Pb and A1 0 while Pb/Pt ratio ranged from 0.3 to- 5.0.

After 20 cc. of the catalyst thus obtained were heated at 500 C. under a hydrogen stream for an hour, there was passed through a layer of the catalyst maintained at 490 C. a mixed gas consisting of hydrogen and n-heptane in a molar ratio of 3:1 at an LHSV of 0.5 hr. under an atmospheric pressure.

The reaction results were as tabulated in Table I following.

The data shown in Table I are also shown graphically in the accompanying Figure.

6. Comparative Example 1 Twenty milliliters of a known catalyst consisting of 0.5% platinum and 99.5 'y-alumina were heated under hydrogen at 500 C. for 1 hour. Through the catalyst layer,

was passed a gaseous mixture of hydrogen and n-heptane at an LHSV of 0.5 hr.- under atmospheric pressure,-

while maintaining the layer at 510 C. Molar yields of the products were: Benzene 8.7%, toluene 36.7%, xylenes 3.8% and the total aromatics 49.2% after a reaction time of 1 hour.

Comparative Example 2 Composition of the naphtha source (percent by volume):

Parafiins 48.3 Olefins 0.4 Naphthenes 38.6 Aromatics 12.7

What is claimed is:

1. Method of producing aromatic hydrocarbons which comprises hydroforming a mixture of hydrogen and a hydrocarbon over a catalyst at a temperature of from 300 C. to 650 C. under a pressure of from 5 to 20 kg./cm. said catalyst consisting essentially of from about 0.01 to about 5 weight percent of platinum and from about 0.01 to about 5 weight percent of lead, up to about 1% by weight of a component selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, zinc, cadmium, mercury, germanium, bismuth, chromium, molybdenum, tungsten, uranium, rhenium, ruthenium, rhodium, palladium, osmium and iridium, up to 2.0% by weight of a halogen and a carrier, wherein the ratio of lead to platinum is from 0.1 to 7, and being prepared by coprecipitating said platinum and lead components upon a carrier.

2. Method according to Claim 1 wherein said hydrocarbon is a member selected from the group consisting of naphtha, kerosene and light oil.

3. Method according to Claim 1 wherein said hydroforming is carried out under reaction conditions including a temperature ranging from 430 C. to 580 C., and an LHSV ranging from 0.2 to 10 hrf 4. Method according to Claim 1 wherein said platinum component is a compound of platinum and halogen.

5. Method according to Claim 1 wherein the halogen is chlorine and the amount of chlorine contained in the catalyst is in the range of 0.1-2.0% by weight based on the total weight of catalyst components. 3

6. Method according to Claim 1 wherein said carrier is a member selected from the group consisting of alumina, alumina hydrate, alumina gel and silica-alumina.

7. Method according to Claim 1 wherein said catalyst is treated with hydrogen-containing gas in the vicinity of the reaction temperature prior to hydroforming. 3

8. Method according to Claim 1 wherein said catalyst contains from about 0.1 to about 1 wt. percent platinum and from about 0.1 to about 3 wt. percent lead, the ratioof lead to platinum is 0.3-3.0, and said hydroformingjis carried out under a pressure ranging from 5-15 kg./cn"1.

9. Method of Claim 1, wherein said catalyst is prepared by supporting platinum and lead on the carrie by gel formation.

10. Method of producing aromatic hydrocarbons which comprises hydroforming a mixture of hydrogen and a hydrocarbon over a catalyst at a temperature of from 300' C. to 650 C. under a pressure of from 5 to 20 kg./ cm, said catalyst consisting essentially of from about 0.01 to about 5 weight percent of platinum and from about 0.01 to about 5 weight percent of lead and a carrier, wherein the ratio of lead to platinum is from 0.1 to 7, and being prepared by coprecipitating said platinum and lead components upon a carrier,

References Cited UNITED STATES PATENTS 8 Patrick et a1. 260-672 R Drehman et al. 260-6833 Fuller et al. 260-6735 Stirton 260-668 Fleck et a1. 260-668 Murray et a1. 208-90 Wilhelm 208-111 DELBERT E. GANTZ, Primary Examiner 10 S. L. BERGER, Assistant Examiner US. Cl. X.R.

208-138; 252-441, 455 R, 466 PT 

